What can cause difficulty swallowing in an 80 years old who has a colostomy bag?

Unrelated: Swallowing difficulties can occur as a person ages. Need to see a doctor for a swallowing evaluation. If the colostomy surgery was recent, then the stress of the surgery & weakness during recovery from a major surgery can temporarily affect swallowing. Still needs a swallowing evaluation to identify a source of the problem.

I don't think: Difficulty in swallowing has anything to do with colostomy. It can be a mechanical obstruction or difficulty with muscle coordination or strength. Get to a doctor, because if he aspirates his food or gastric contents, it can be a serious problem.